In general, a refrigerator is mainly divided into two types such as a constant speed refrigerator which performs cooling by turning on or off a compressor and an inverter-controlled refrigerator which performs cooling by an inverter varying speed of the compressor. In these days while energy saving is strongly demanded, the inverter-controlled refrigerator is mostly used. In contrast, some countries strongly demand the constant speed refrigerator which can be provided at low cost.
However, these countries which strongly demand the constant speed refrigerator are also increasingly aware of power saving. Accordingly, there is a gradually increased demand for the inverter-controlled refrigerator having excellent energy saving efficiency.
The inverter-controlled refrigerator is much more expensive than the constant speed refrigerator. Accordingly, whether or not the inverter-controlled refrigerator is popularly distributed depends on how an inexpensive refrigerator can be provided, and further depends on how frequently and quickly the inverter-controlled refrigerator can be provided in response to a demand situation.
Therefore, the present applicant has progressively studied a method in which the constant speed refrigerator is utilized so as to function as a simple inverter-controlled refrigerator.
The present applicant has already proposed that a main body control unit of the constant speed refrigerator is replaced with an inverter control unit which can perform variable speed control on the compressor by inputting only a temperature signal from a thermistor so as to function as the inverter-controlled refrigerator (for example, refer to PTL 1).
FIG. 13 is a view illustrating a configuration of a refrigerator in the related art disclosed in PTL 1.
The refrigerator includes main body control unit 101. A temperature signal is input to main body control unit 101 from thermistor 103 disposed in storage 102. Main body control unit 101 is an inverter control unit which variably controls a rotation speed of compressor 104, based on the temperature signal, specifically, a time change or a temperature change. Main body control unit 101 (hereinafter, referred to as an inverter main body control unit) having an inverter system as described above controls compressor 104 and each component such as cooling fan 105 for circulating cool air and condenser fan 106.
Instead of the constant speed main body control unit which controls the compressor and the cooling fan to be turned on or off by using a thermostat, the refrigerator configured in this way in the related art has inverter main body control unit 101 which can perform variable speed control on compressor 104 by inputting the temperature signal from thermistor 103. In this manner, the refrigerator functions as the inverter-controlled refrigerator.
According to the refrigerator disclosed in PTL 1, it is not necessary to install a complicated electronic circuit for processing an operation status of a freezing system. Therefore, there is an advantage in that the refrigerator functioning as the inverter-controlled refrigerator can be provided at low cost.
However, according to the configuration disclosed in PTL 1, when the refrigerator functions as the inverter-controlled refrigerator, inverter main body control unit 101 which variably controls the rotation speed of the compressor by using the temperature signal from the thermistor has to be newly developed and designed as the main body control unit of the refrigerator, thereby causing work to be carried out in order to attach inverter main body control unit 101 to a refrigerator main body as the main body control unit.
That is, a refrigerator manufacturer side has to newly perform a development step of controlling a huge inverter main body and a complicated assembly step of attaching the main body control unit, thereby requiring time and effort. Consequently, there is a problem in that the inverter-controlled refrigerator is less likely to be provided frequently and quickly.
Particularly when the refrigerator is assembled, inverter main body control unit 101 and thermistor 103 are newly attached and connected to each other using a lead wire. Furthermore, it becomes necessary to connect inverter main body control unit 101 to each component such as cooling fan 105 and condenser fan 106. In this way, the refrigerator manufacturer needs to perform a lot of steps, and the refrigerator manufacturer cannot easily manufacture the inverter-controlled refrigerator. Accordingly, there is a problem to be solved in order to enable the refrigerator manufacturer to frequently and quickly supply the inverter-controlled refrigerator.
Even if a function of the inverter-controlled refrigerator is realized in this way, for example, the compressor has different rotation speeds at which the efficiency of the compressor for each compression capacity is optimized. Accordingly, in some cases, the rotation speed set by the inverter based on an output of the thermistor is not always the rotation speed which can optimize the efficiency of the compressor. Therefore, there is also a problem in that an energy saving benefit obtained by the inverter system cannot sufficiently be utilized.